JP6710150B2 - Construction machinery - Google Patents

Description

The present invention relates to a construction machine such as a hydraulic excavator.

In recent years, energy saving has become an important development item in construction machines such as hydraulic excavators and wheel loaders. Energy saving of the hydraulic system itself is important for energy saving of construction machinery, and application of a hydraulic closed circuit system in which a hydraulic pump and a hydraulic actuator are connected to form a closed circuit is under study. In this hydraulic closed circuit system, since the control valve is not provided between the hydraulic pump and the hydraulic actuator, there is no pressure loss due to the control valve, and there is no flow rate loss because the hydraulic pump discharges only the required flow rate.

As a background art of a construction machine equipped with this type of hydraulic closed circuit system, Patent Document 1 is configured to connect any one of a plurality of variable displacement hydraulic pumps and one of a plurality of hydraulic actuators. The configuration of a hydraulic closed circuit system including a plurality of closed circuits in which pressure oil circulates between a variable displacement hydraulic pump and a hydraulic actuator is described.

On the other hand, as a background art of a large hydraulic excavator, Patent Document 2 describes a configuration of a hydraulic excavator in which a hydraulic system is driven by two prime movers.

U.S. Patent Application Publication No. 2016/0032565 JP-A-11-124879

In a large hydraulic excavator equipped with two prime movers as in Patent Document 2, if all hydraulic actuators are operated by a plurality of hydraulic pumps connected to one prime mover, two provisional hydraulic excavators will be provided. Even if one of the prime movers becomes inoperable due to a failure or the like, the other one can maintain the minimum operation of the hydraulic excavator. On the other hand, even for a large hydraulic excavator equipped with two prime movers, there is a demand to apply the hydraulic closed circuit system as disclosed in Patent Document 1 in order to save energy.

However, if the hydraulic closed circuit system of Patent Document 1 is applied to the hydraulic system in which all the hydraulic actuators are driven by one prime mover, the number of hydraulic pumps and electromagnetic switching valves increases, which makes the hydraulic system complicated and large. There will be a new issue of becoming a reality.

Therefore, according to the present invention, in a construction machine in which a plurality of hydraulic pumps are driven by at least two prime movers to operate a plurality of hydraulic actuators, one prime mover operates while saving energy and downsizing the hydraulic system. Even if it becomes impossible, it is an object to ensure the minimum operation of the hydraulic actuator.

In order to solve the above problems, for example, the configurations described in the claims are adopted. The present application includes a plurality of means for solving the above problems. To give an example thereof, a first prime mover, a first hydraulic drive device driven by the first prime mover, and a supply from the first hydraulic drive device are provided. A plurality of first hydraulic actuators that operate with pressure oil, a second prime mover, a second hydraulic drive device that is driven by the second prime mover, and a plurality that operate with pressure oil supplied from the second hydraulic drive device. And a plurality of first closed circuit pumps and a plurality of first open circuit pumps connected to the first prime mover, and the plurality of second hydraulic actuators. A plurality of hydraulic circuits in which any one of the first hydraulic actuators and any one of the plurality of first closed circuit pumps are connected to circulate the pressure oil between the first hydraulic actuator and the first closed circuit pumps. The first closed circuit, and any one of the plurality of first closed circuits and one of the plurality of first open circuit pumps are connected to each other, and the first closed circuit pump is connected to the first closed circuit. A plurality of first assist flow paths for supplying pressure oil to the second hydraulic drive device, the second hydraulic drive device being connected to the second prime mover; and a plurality of second closed circuit pumps and a plurality of second open circuit pumps. And any one of the plurality of second hydraulic actuators and any one of the plurality of second closed circuit pumps, and a pressure is applied between the second hydraulic actuator and the second closed circuit pump. A plurality of second closed circuits in which oil circulates, any one of the plurality of second closed circuits, and any one of the plurality of second open circuit pumps are connected to each other, and A plurality of second assist flow passages for supplying pressure oil to the second closed circuit, and further branching from any one of the plurality of first assist flow passages, At least one first emergency switching flow path that supplies pressure oil to the second closed circuit from the first open circuit pump that is connected to any one of the closed circuits and that is connected to the first assist flow path; , A first assist switching device for guiding the pressure oil flowing through the first assist flow channel to the first emergency switching flow channel, and a branch from any one of the plurality of second assist flow channels, At least one second emergency circuit that supplies pressure oil to the first closed circuit from the second open circuit pump that is connected to any one of the plurality of first closed circuits and that is connected to the second assist flow path. Switching channel, a second assist switching device for guiding the pressure oil flowing through the second assist channel to the second emergency switching channel, and the first assist switching And a control device for controlling the operation of the device and the second assist switching device.

According to the present invention, in a construction machine in which a plurality of hydraulic pumps are driven by at least two prime movers to operate a plurality of hydraulic actuators, one prime mover operates while saving energy and downsizing the hydraulic system. Even if it becomes impossible, the minimum operation of the hydraulic actuator can be ensured. The problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a side view of the hydraulic excavator which concerns on 1st Embodiment of this invention. It is a hydraulic circuit diagram showing a hydraulic drive system and a control system for driving the hydraulic excavator according to the first embodiment of the present invention. It is the schematic which shows the flow of the pressure oil at the time of the normal operation of the hydraulic circuit in 1st Embodiment of the construction machine of this invention. It is a schematic diagram showing a flow of pressure oil at the time of engine failure of one side of a hydraulic circuit in a 1st embodiment of a construction machine of the present invention (at the time of inoperability). It is a conceptual diagram which shows the structure of the control apparatus which comprises 1st Embodiment of the construction machine of this invention. It is a flowchart figure which shows the processing content of the flow path calculating part of the control apparatus which comprises 1st Embodiment of the construction machine of this invention. It is a schematic diagram showing a hydraulic drive which constitutes a 2nd embodiment of the construction machine of the present invention. It is the schematic which shows the flow of the pressure oil at the time of the normal operation of the hydraulic circuit in 2nd Embodiment of the construction machine of this invention. It is the schematic which shows the flow of the pressure oil at the time of one side engine failure (at the time of an inoperability) of the hydraulic circuit in 2nd Embodiment of the construction machine of this invention. It is a conceptual diagram which shows the structure of the control apparatus which comprises 2nd Embodiment of the construction machine of this invention. It is a flowchart figure which shows the processing content of the flow path calculating part of the control apparatus which comprises 2nd Embodiment of the construction machine of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings by taking a large hydraulic excavator as an example of a construction machine. In the present invention, two or more prime movers are mounted, a closed circuit pump and a hydraulic cylinder are connected to form a closed circuit, an open circuit pump is connected to the closed circuit, and the open circuit pump is connected to the hydraulic cylinder. The present invention can be applied to all construction machines provided with a hydraulic closed circuit system capable of supplying hydraulic oil to the head-side oil chamber, and the application of the present invention is not limited to hydraulic excavators.

<First Embodiment>
FIG. 1 is a side view of a hydraulic excavator according to a first embodiment of the present invention. In the description below, the front, rear, left, and right directions are defined by the operator operating the hydraulic excavator. Therefore, for example, the left-right direction in FIG. 1 is the front-back direction of the hydraulic excavator.

As shown in FIG. 1, a hydraulic excavator 100 according to the present embodiment has a lower traveling body (traveling body) 103 provided with crawler type traveling devices 8a and 8b on both sides in the left-right direction, and a swing structure on the lower traveling body 103. And an upper revolving structure 102 that is movably attached. A cab 101 on which an operator rides is provided on the upper swing body 102.

A front working machine (working machine) 104 for performing, for example, excavation work is attached to the front side of the upper-part turning body 102 so as to be able to lift and lower. The front working machine 104 drives the boom 2, a single rod type boom cylinder 1 that drives the boom 2, an arm 4, a single rod type arm cylinder 3 that drives the arm 4, a bucket 6, and a bucket 6. And a single rod type bucket cylinder 5. In the boom cylinder 1, the tip end portion of the boom rod 1b is connected to the upper swing body 102, and the base end portion of the boom head 1a is connected to the boom 2. In the arm cylinder 3, the tip end of the arm rod 3b is connected to the arm 4, and the arm head 3a of the arm cylinder 3 is connected to the boom 2. In the bucket cylinder 5, the tip end portion of the bucket rod 5b is connected to the bucket 6, and the base end of the bucket head 5a of the bucket cylinder 5 is connected to the arm 4.

The cab 101 is provided with an operating device 19 (see FIG. 2) for traveling/turning operations and operating the boom 2, arm 4, and bucket 6. The operating device 19 includes a plurality of operating levers 19a to 19d. The operating lever 19a moves forward/backward of the traveling device 8a on the left side, the operating lever 19b advances/retracts the traveling device 8b on the right side, the operating lever 19c rotates the upper revolving structure 102, and extends/bends the arm 4 of the arm 4, The operation lever 19d is used by the operator to instruct boom raising/boom lowering operations of the boom 2 and bucket excavation/bucket opening operations of the bucket 6.

Next, the system configuration of the hydraulic drive system for driving the hydraulic excavator 100 will be described with reference to FIG. FIG. 2 is a hydraulic circuit diagram showing a hydraulic drive system and a control system for driving the hydraulic excavator. In the following description, a closed circuit connecting ◯ and □ will be referred to as a closed circuit ◯−□. For example, the closed circuit 11-1 is a closed circuit that connects the closed circuit pump 11 and the boom cylinder 1.

As shown in FIG. 2, in the present embodiment, an engine (first prime mover) 9a, a first hydraulic drive device HD1 driven by the power transmitted from the engine 9a via a transmission device 10a, and a first hydraulic drive device. Boom cylinder (first hydraulic actuator) 1 and arm cylinder (first hydraulic actuator) 3, which are operated by pressure oil supplied from HD1, engine (second prime mover) 9b, and transmission from engine 9b through transmission device 10b A second hydraulic drive device HD2 that is driven by the generated power, a bucket cylinder (second hydraulic actuator) 5 and a hydraulic motor (second hydraulic actuator) 7 that operate with pressure oil supplied from the second hydraulic drive device HD2, Equipped with.

Although only one hydraulic motor 7 is shown in FIG. 2, one hydraulic motor 7 is actually used to drive the upper swing body 102, and one hydraulic motor 7 is used to drive the left and right traveling devices 8a and 8b. Two hydraulic motors (hydraulic actuators) 7 are provided.

The first hydraulic drive device HD1 includes two closed circuit pumps (first closed circuit pumps) 11 and 12 connected to the engine 9a, two open circuit pumps (first open circuit pumps) 15 and 16, and a closed circuit pump. Four closed circuits configured by connecting 11 and each of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 via a flow path switching valve (first closed circuit switching device) 21a. The closed circuit pump 12 and four closed circuits configured by connecting the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 via the flow path switching valve 21a.

More specifically, the first hydraulic drive device HD1 includes a closed circuit 11-1 and a closed circuit 12-3 corresponding to the “first closed circuit” of the present invention, as well as a closed circuit 11-3 and a closed circuit 11. -5, a closed circuit 11-7, a closed circuit 12-1, a closed circuit 12-5, and a closed circuit 12-7 (first emergency closed circuit). The closed circuit to which the pressure oil flows is determined by the operation of the flow path switching valve 21a. The operation of the flow path switching valve 21a is controlled by a control signal from the control device 20.

The first hydraulic drive device HD1 is connected to a closed circuit (for example, the closed circuit 11-1) including the closed circuit pump 11 and supplies the pressure oil from the open circuit pump 15 to the assist passage (the first hydraulic drive device HD1). 1 assist flow path) 40, and an emergency switching flow path (first emergency switching flow path) 50 that branches from the assist flow path 40 and supplies the pressure oil from the open circuit pump 15 to the arm cylinder 3. Further, the first hydraulic drive device HD1 is connected to a closed circuit (for example, a closed circuit 12-3) including the closed circuit pump 12, and an assist flow path (the first hydraulic circuit) that supplies pressure oil from the open circuit pump 16 (first 1 assist flow path) 41, and an emergency switching flow path (first emergency switching flow path) 51 that branches from the assist flow path 41 and supplies the pressure oil from the open circuit pump 16 to the bucket cylinder 5.

The assist passages 40 and 41 are provided with assist valves 23a and 24a, respectively, and the emergency switching passages 50 and 51 are provided with auxiliary control valves 26a and 27a, respectively. By closing the assist valves 23a and 24a and opening the auxiliary control valves 26a and 27a, the pressure oil from the open circuit pumps 15 and 16 can be supplied to the arm cylinder 3 and the bucket cylinder 5, respectively. The opening and closing of the assist valves 23a and 24a and the auxiliary control valves 26a and 27a or the flow passage connection direction are controlled according to the control command value from the control device 20. The assist valves 23a and 24a and the auxiliary control valves 26a and 27a correspond to the "first assist switching device" of the present invention.

Further, the pressure oil from the arm cylinder 3 returns to the tank (working oil tank) 25 from the working oil return passage 61 via the auxiliary control valve 26a. Similarly, the pressure oil from the bucket cylinder 5 returns to the tank 25 from the hydraulic oil return flow path (first hydraulic oil return flow path) 62 via the auxiliary control valve 27a.

Similarly, for the second hydraulic drive device HD2, two closed circuit pumps (second closed circuit pumps) 13 and 14 and two open circuit pumps (second open circuit pumps) 17 and 18 connected to the engine 9b, The closed circuit pump 13 is connected to each of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 via a flow path switching valve (second closed circuit switching device) 21b. A closed circuit, a closed circuit pump 14, four closed circuits configured by connecting the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 via the flow path switching valve 21b. Have.

More specifically, the second hydraulic drive device HD2 includes the closed circuit 13-1 (second emergency circuit) in addition to the closed circuit 13-5 and the closed circuit 14-7 corresponding to the “second closed circuit” of the present invention. Closed circuit), a closed circuit 13-3, a closed circuit 13-7, a closed circuit 14-1, a closed circuit 14-3, and a closed circuit 14-5. The closed circuit to which the pressure oil flows is determined by the operation of the flow path switching valve 21b. The operation of the flow path switching valve 21b is controlled by a control signal from the control device 20.

In addition, the second hydraulic drive device HD2 is connected to a closed circuit (for example, a closed circuit 13-5) including the closed circuit pump 13, and an assist flow path (second 2 assist flow path) 42, and an emergency switching flow path (second emergency switching flow path) 52 that branches from the assist flow path 42 and supplies the pressure oil from the open circuit pump 17 to the arm cylinder 3. In addition, the second hydraulic drive device HD2 is connected to a closed circuit (for example, a closed circuit 14-7) including the closed circuit pump 14, and an assist flow path (first 2 assist flow path) 43, and an emergency switching flow path (second emergency switching flow path) 53 that branches from the assist flow path 43 and supplies the pressure oil from the open circuit pump 18 to the bucket cylinder 5.

The assist passages 42 and 43 are provided with assist valves 23b and 24b, respectively, and the emergency switching passages 52 and 53 are provided with auxiliary control valves 26b and 27b, respectively. By closing the assist valves 23b and 24b and opening the auxiliary control valves 26b and 27b, the pressure oil from the open circuit pumps 17 and 18 can be supplied to the arm cylinder 3 and the bucket cylinder 5, respectively. These assist valves 23b, 24b and auxiliary control valves 26b, 27b are controlled in their opening/closing or flow passage connection directions according to a control command value from the control device 20. The assist valves 23b and 24b and the auxiliary control valves 26b and 27b correspond to the "second assist switching device" of the present invention.

Further, the pressure oil from the arm cylinder 3 returns to the tank 25 from the hydraulic oil return flow passage (second hydraulic oil return flow passage) 63 via the auxiliary control valve 26b. Similarly, the pressure oil from the bucket cylinder 5 returns to the tank 25 from the hydraulic oil return flow path 64 via the auxiliary control valve 27b.

The closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18 each include a tilting swash plate mechanism having a pair of input/output ports, and a regulator 11a to adjust the tilt angle of the swash plate to adjust the pump displacement. 18a. The regulators 11a to 18a control the discharge flow rates and discharge directions of the closed circuit pumps 11 to 14 and the discharge flow rates of the open circuit pumps 15 to 18 according to the pump discharge flow rate command value received from the control device 20 via the signal line. To do. The intake ports of the open circuit pumps 15 to 18 are connected to the tank 25.

Next, details of the control device 20 will be described with reference to FIG. FIG. 5 is a block diagram showing details of the control device 20. As shown in FIG. 5, the control device 20 includes an operation amount detection unit 20a, an engine failure detection unit 20b, a flow rate calculation unit 20c, a pump/valve control unit 20d, and an emergency circuit control unit 20e. The operation levers 19a to 19d are connected to the control device 20 via signal lines. The operation amount detection unit 20a detects the operation amounts of the operation levers 19a to 19d.

The engine failure detection unit 20b has a function of detecting a failure of the engines 9a and 9b. For example, when the engine failure detection unit 20b measures the engine speeds of the engines 9a and 9b input from an engine speed detector (not shown), and the speed is lower than a preset target engine speed, Judge as a failure.

The flow rate calculation unit 20c, based on the operation amount from the operation amount detection unit 20a and the information from the engine failure detection unit 20b, each hydraulic actuator (that is, boom cylinder 1, arm cylinder 3, bucket cylinder 5, hydraulic motor 7). Determine the control flow rate of. The details of the flow rate calculation unit 20c will be described later.

The pump/valve control unit 20d controls each device according to the discharge flow rate command values of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18 received from the flow rate calculation unit 20c and the control command values of the flow path switching valves 21a and 21b. Outputs a control command signal.

The emergency circuit control unit 20e follows the control command values of the assist valves 23a, 23b, 24a, and 24b and the control command values of the auxiliary control valves 26a, 26b, 27a, and 27b received from the flow rate calculation unit 20c for each device. Outputs a control command signal.

Next, details of the flow rate calculation unit 20c will be described with reference to FIG. FIG. 6 is a flowchart showing the processing contents of the flow path calculation unit. As shown in FIG. 6, in step S1, if the operation amount from the operation amount detection unit 20a is larger than 0, the process proceeds to step S2. On the other hand, when the manipulated variable is 0, the process proceeds to step S4, the discharge flow rate command values of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18 are set to 0, and the flow path switching valves 21a and 21b are controlled. Set the command value to closed. Further, the control command values of the assist valves 23a to 24b are set to open, and the control command values of the auxiliary control valves 26a to 27b are set to closed.

When it is determined in step S2 that the engines 9a and 9b are normal based on the information from the engine failure detection unit 20b, the process proceeds to step S3. On the other hand, when it is determined that one of the engine 9a and the engine 9b is out of order, the process proceeds to step S5, and the engine operates normally among the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18 which are proportional to the operation amount. The discharge flow rate command value is set based on the operation amount of the operation levers 19a to 19d. The control command values of the flow path switching valves 21a and 21b on the side where the engine is normally operating are set to open/close so as to connect the pump and the actuator, corresponding to the operation commands of the operation levers 19a to 19d. Further, the control command values of the assist valves 23a, 23b, 24a, 24b are set to be closed, and the control command values of the auxiliary control valves 26a to 27b are set to be open in response to the operation commands of the operation levers 19a to 19d. Note that, for example, when one of the engines fails, the information on the engine failure may be displayed to the operator once on a monitor and the operator's approval, and then step S5 may be executed.

In step S3, the discharge flow rate command values of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18 which are proportional to the operation amount are set, and the actuators and the closed circuit pumps corresponding to the operation commands of the operation levers 19a to 19d are set. The control command values of the flow path switching valves 21a and 21b are set to open/close so that 11 to 14 and the open circuit pumps 15 to 18 are connected. At this time, the control command values of the assist valves 23a, 23b, 24a, 24b are set to open, and the control command values of the auxiliary control valves 26a to 27b are set to closed.

Next, the operation of the hydraulic drive system according to the first embodiment will be described. First, the state of the hydraulic circuit when both engines 9a and 9b are operating normally will be described. When the operator operates all the operation levers 19a to 19d and gives an input for driving the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7, the operation amount detection unit 20a in the control device 20 causes the operation lever 19a to operate. A manipulated variable of ˜19d is received via the signal line. The engine failure detection unit 20b acquires the operation information of the engines 9a and 9b via a signal line and determines whether the engines 9a and 9b are operating normally.

As shown in FIG. 6, when the engines 9a and 9b are operating normally, the flow rate calculation unit 20c proceeds to step S3, and multiplies the manipulated variable by, for example, a preset proportional gain to close the circuit pumps 11 to 11. 14 and open circuit pumps 15 to 18 as discharge flow rate command values, and closed circuit pump 11 and boom cylinder 1, closed circuit pump 12 and arm cylinder 3, closed circuit pump 13 and bucket cylinder 5, and closed circuit pump 14. The control command values of the flow path switching valves 21a and 21b are set so that the hydraulic motor 7 and the hydraulic motor 7 are connected by the flow path. Further, the flow rate calculation unit 20c sets the control command values of the assist valves 23a, 23b, 24a, 24b to open and sets the control command values of the auxiliary control valves 26a to 27b to close.

The pump/valve control unit 20d outputs control signals to the closed circuit pumps 11 to 14, the open circuit pumps 15 to 18, and the flow path switching valves 21a and 21b according to the control command value from the flow rate calculation unit 20c. Further, the emergency circuit control unit 20e outputs an open control signal to the assist valves 23a, 23b, 24a and 24b and a close control signal to the auxiliary control valves 26a to 27b according to the control command value from the flow rate calculation unit 20c.

FIG. 3 shows the flow of pressure oil in the hydraulic circuit during normal operation. The thick line in the figure indicates that it is a circuit through which pressure oil flows. Each of the regulators 11a to 18a receives a control signal from the pump/valve control unit 20d via a signal line, and controls the discharge flow rates of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18. The closed circuit pump 11 discharges hydraulic oil to the boom head 1a of the boom cylinder 1 via the flow path switching valve 21a to extend the boom cylinder 1 (closed circuit 11-1). At this time, the hydraulic oil discharged by the open circuit pump 15 merges with the hydraulic oil discharged by the closed circuit pump 11 via the assist valve 23a, and then flows into the boom head 1a via the flow path switching valve 21a ( Assist channel 40).

The closed circuit pump 12 discharges hydraulic oil to the arm head 3a of the arm cylinder 3 via the flow path switching valve 21a to extend the arm cylinder 3 (closed circuit 12-3). At this time, the hydraulic oil discharged by the open circuit pump 16 merges with the hydraulic oil discharged by the closed circuit pump 12 via the assist valve 24a, and then flows into the arm head 3a via the flow path switching valve 21a ( Assist channel 41).

The closed circuit pump 13 discharges the hydraulic oil to the bucket head 5a of the bucket cylinder 5 via the flow path switching valve 21b to extend the bucket cylinder 5 (closed circuit 13-5). At this time, the hydraulic oil discharged by the open circuit pump 17 merges with the hydraulic oil discharged by the closed circuit pump 13 via the assist valve 23b, and then flows into the bucket head 5a via the flow path switching valve 21b ( Assist channel 42).

The closed circuit pump 14 discharges hydraulic oil to the hydraulic motor 7 via the flow path switching valve 21b to rotate the hydraulic motor 7 (closed circuit 14-7). At this time, the hydraulic oil discharged by the open circuit pump 18 merges with the hydraulic oil discharged by the closed circuit pump 14 via the assist valve 24b, and then flows into the hydraulic motor 7 via the flow path switching valve 21b ( Assist channel 43). As a result, all actuators of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 are simultaneously driven by the two engines 9a and 9b.

Next, the state of the hydraulic circuit when the engine on one side cannot operate will be described. Here, a case where an abnormality occurs in the engine 9b is assumed and described. When it is determined that the engine 9b is out of order, the flow rate calculation unit 20c proceeds to step S5 in FIG. 6 and opens the operation amount multiplied by, for example, a preset proportional gain with the closed circuit pumps 11 and 12. The discharge flow rate command values of the circuit pumps 15 and 16 are set, and the discharge flow rate command values of the closed circuit pumps 13 and 14 and the open circuit pumps 17 and 18 are set to zero.

Further, the control command value of the flow passage switching valve 21a is set so that the closed circuit pump 11 and the boom cylinder 1 and the closed circuit pump 12 and the hydraulic motor 7 are connected by the flow passage. At this time, a closing command value is set in the flow path switching valve 21b.

The flow rate calculation unit 20c sets the control command value of the assist valves 23a, 23b, 24a, 24b to closed, and opens the auxiliary control valves 26a, 27a according to the operation direction and operation amount instructed by the operation levers 19c, 19d. Set the command value. Further, the control command values of the auxiliary control valves 26b and 27b are set to be closed.

The pump/valve control unit 20d outputs control signals to the closed circuit pumps 11 to 14, the open circuit pumps 15 to 18, and the flow path switching valves 21a and 21b according to the control command value from the flow rate calculation unit 20c. Further, the emergency circuit control unit 20e outputs a close control signal to the assist valves 23a, 23b, 24a and 24b and an open control signal to the auxiliary control valves 26a to 27b according to the control command value from the flow rate calculation unit 20c.

FIG. 4 shows the flow of pressure oil in the hydraulic circuit when the engine 9b cannot operate. The thick line in the figure indicates that it is a circuit through which pressure oil flows. The regulators 11a to 18a respectively receive control signals from the pump/valve control unit 20d via signal lines, and control the discharge flow rates of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18. The closed circuit pump 11 discharges hydraulic oil to the boom head 1a of the boom cylinder 1 via the flow path switching valve 21a to extend the boom cylinder 1 (closed circuit 11-1). The closed circuit pump 12 discharges hydraulic oil to the hydraulic motor 7 via the flow path switching valve 21a to rotate the hydraulic motor 7 (closed circuit 12-7: first emergency closed circuit).

On the other hand, the hydraulic fluid discharged by the open circuit pump 15 flows into the arm head 3a via the auxiliary control valve 26a, and extends the arm cylinder 3 (emergency switching flow path 50). The hydraulic oil discharged by the open circuit pump 16 flows into the bucket head 5a via the auxiliary control valve 27a, and extends the bucket cylinder 5 (emergency switching flow path 51). As a result, all the hydraulic actuators of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 are simultaneously driven by the single engine 9a.

Next, operation effects of the hydraulic excavator according to the present embodiment will be described. If you want to drive four hydraulic actuators even when one engine becomes inoperable by applying the conventional hydraulic closed circuit system to the hydraulic circuit device of a large hydraulic excavator equipped with two engines, Four closed circuit pumps were required to drive all four actuators for one engine. However, in the present embodiment, when the engine is inoperable, the open circuit pump connected to the closed circuit is connected to the closed circuit connected to the inoperable engine so that the open circuit pump separates another hydraulic pressure. Since the actuator is configured to operate, the number of closed circuit pumps can be halved. Also, by reducing the number of closed circuit pumps, the routing of hydraulic piping is simplified.

In other words, in the present embodiment, even if one of the two engines becomes inoperable, the remaining one can perform the minimum combined operation of the four hydraulic actuators, so that, for example, engine trouble may occur. Even if it occurs, it is possible to retract the hydraulic excavator, return the front work implement 104 to a stable posture, and perform a minimum emergency operation. Moreover, since the number of closed circuit pumps can be reduced, the installation of hydraulic piping can be simplified. Further, in this embodiment, when the engine 9b cannot operate, the closed circuit pumps 11 and 12 drive the boom cylinder 1 and the hydraulic motor 7, and the open circuit pumps 15 and 16 drive the arm cylinder 3 and the bucket cylinder 5. Since the configuration is adopted, there is also an advantage that the behavior of the four complex operations at the time of abnormality is stable.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. In the following description, the same components as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted.

The second embodiment is mainly different from the first embodiment in that the assist valves 23a to 24b of the first embodiment shown in FIG. 3 are not used. FIG. 7 is a hydraulic circuit diagram showing a hydraulic drive system and a control system for driving the hydraulic excavator according to the second embodiment.

As shown in FIG. 7, in the second embodiment, the discharge side flow paths of the open circuit pumps 15 and 16 are connected to the flow path switching valve (first closed circuit switching device) 21c, and the open circuit pumps 17 and 18 are also connected. The discharge side is connected to a flow path switching valve (second closed circuit switching device) 21d. The flow path switching valves 21c and 21d are connected to the closed circuit pumps 11 to 14 and one of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 according to the control command value received from the control device 20 via the signal line. The open circuit pumps 15 to 18 are connected to the boom head 1a, the arm head 3a, and the bucket head 5a, and the closed circuit pumps 11 to 14 discharge the hydraulic oil discharged by the open circuit pumps 15 to 18. It has the function of merging with the discharged hydraulic oil.

Further, the flow paths branched from the discharge side flow paths of the open circuit pumps 15 to 18 are connected to the arm rods via rod assist valves (first assist switching device, second assist switching device) 28a, 29a, 28b, 29b, respectively. 3b, connected to the bucket rod 5b. Opening/closing of the rod assist valves 28a, 29a, 28b, 29b is controlled by a control command value received from the control device 20 via a signal line.

A flushing valve 30a is connected to branch from the flow path connected to the arm head 3a and the arm rod 3b. The flushing valve 30a is connected to the low pressure side flow path of the flow paths connected to the flushing valve 30a. The tank 25 is connected via a hydraulic oil return flow path (second hydraulic oil return flow path) 65. Further, the flushing valve 30b is connected to the flow path connected to the bucket head 5a and the bucket rod 5b, and the flushing valve 30b is connected to the flushing valve 30b. The passage and the tank 25 are connected via a hydraulic oil return flow passage (first hydraulic oil return flow passage) 66.

Next, the operation of the hydraulic drive system according to the second embodiment will be described. First, the state of the hydraulic circuit when both engines 9a and 9b are operating normally will be described with reference to FIG. When the operator operates all the operation levers 19a to 19d to give inputs for driving the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 in the extension direction and driving the hydraulic motor 7 to rotate to the right, the operation amount detection unit 20a in the control device 20. Receives the operation amount of the operation levers 19a to 19d via a signal line. The engine failure detection unit 20b acquires the operation information of the engines 9a and 9b via a signal line and determines whether the engines 9a and 9b are operating normally. The flow rate calculation unit 20c determines the control flow rate of each actuator based on the operation amount from the operation amount detection unit 20a and the information from the engine failure detection unit 20b.

Next, details of the flow rate calculation unit 20c will be described with reference to FIG. FIG. 11 is a flowchart showing a procedure of control processing in the second embodiment. When the engines 9a and 9b are normally operating, the process proceeds to step S3, and the discharge flow rate command of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18 is obtained by multiplying the operation amount by, for example, a preset proportional gain. It is set as a value, and the closed circuit pump 11 and the boom cylinder 1, the closed circuit pump 12, the arm cylinder 3, the closed circuit pump 13 and the bucket cylinder 5, and the closed circuit pump 14 and the hydraulic motor 7 are connected by a flow path. A control command value for the flow path switching valves 21c and 21d is set.

Further, the flow path switching is performed so that the open circuit pump 15 and the boom head 1a, the open circuit pump 16 and the arm head 3a, the open circuit pump 17 and the bucket head 5a, and the open circuit pump 18 and the hydraulic motor 7 are connected by a flow path. A control command value for the valves 21c and 21d is set. The flow rate calculation unit 20c sets the control command value of the rod assist valves 28a, 29a, 28b, 29b to closed.

The pump/valve control unit 20d outputs control signals to the closed circuit pumps 11 to 14, the open circuit pumps 15 to 18, and the flow path switching valves 21c and 21d according to the control command value from the flow rate calculation unit 20c. Further, the emergency circuit control unit 20e outputs a close control signal to the rod assist valves 28a, 29a, 28b, 29b according to the control command value from the flow rate calculation unit 20c.

FIG. 8 shows the flow of pressure oil in the hydraulic circuit. The thick line in the figure indicates that it is a circuit through which pressure oil flows. Each of the regulators 11a to 18a receives a control signal from the pump/valve control unit 20d via a signal line, and controls the discharge flow rates of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18. The closed circuit pump 11 discharges hydraulic oil to the boom head 1a of the boom cylinder 1 via the flow path switching valve 21c to extend the boom cylinder 1 (closed circuit 11-1). At this time, the hydraulic oil discharged by the open circuit pump 15 merges with the hydraulic oil discharged by the closed circuit pump 11 via the flow path switching valve 21c and flows into the boom head 1a (assist flow path 40).

The closed circuit pump 12 discharges hydraulic oil to the arm head 3a of the arm cylinder 3 via the flow path switching valve 21c, and extends the arm cylinder 3 (closed circuit 12-3). At this time, the hydraulic oil discharged by the open circuit pump 16 flows into the arm head 3a via the flow path switching valve 21c (assist flow path 41).

The closed circuit pump 13 discharges hydraulic oil to the bucket head 5a of the bucket cylinder 5 via the flow path switching valve 21d to extend the bucket cylinder 5 (closed circuit 13-5). At this time, the hydraulic oil discharged by the open circuit pump 17 flows into the bucket head 5a via the flow path switching valve 21d (assist flow path 42).

The closed circuit pump 14 discharges hydraulic oil to the hydraulic motor 7 via the flow path switching valve 21d to rotate the hydraulic motor 7 (closed circuit 14-7). At this time, the hydraulic oil discharged by the open circuit pump 18 flows into the hydraulic motor 7 via the flow path switching valve 21d. (Assist flow path 43) As a result, all the actuators of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 are simultaneously driven by the two engines 9a and 9b.

Next, a case in which the minimum workable state is maintained when the engine 9b on one side in the second embodiment fails (when it cannot operate) will be described with reference to FIGS. 9 to 11.

When the operator operates all the operation levers 19a to 19d to give an input for driving the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 in the extension direction and driving the hydraulic motor 7 to rotate to the right, the operation in the control device 20 shown in FIG. The amount detection unit 20a receives the operation amount of the operation levers 19a to 19d via the signal line.

The engine failure detection unit 20b acquires the operation information of the engines 9a and 9b via a signal line and determines whether the engines 9a and 9b are operating normally. As shown in FIG. 11, when it is determined that the engine 9b is out of order, the flow rate calculation unit 20c proceeds to step S5, and multiplies the manipulated variable by, for example, a preset proportional gain to obtain the closed circuit pump 11, 12 and the open circuit pumps 15 and 16 are set as the discharge flow rate command values, and the closed circuit pumps 13 and 14 and the open circuit pumps 17 and 18 are set to the discharge flow rate command values. Further, the closed circuit pump 11 and the boom cylinder 1, the closed circuit pump 12 and the hydraulic motor 7, the open circuit pump 15 and the arm head 3a, and the open circuit pump 16 and the bucket head 5a are connected by a flow path. The control command value of the path switching valve 21c is set. At this time, the control command value of the flow path switching valve 21d is set to be closed. Further, the flow rate calculation unit 20c sets the control command value of the rod assist valves 28a, 29a, 28b, 29b to open.

The pump/valve control unit 20d outputs control signals to the closed circuit pumps 11 to 14, the open circuit pumps 15 to 18, and the flow path switching valves 21c and 21d according to the control command value from the flow rate calculation unit 20c. Further, the emergency circuit control unit 20e outputs a control signal to the rod assist valves 28a, 29a, 28b, 29b according to the control command value from the flow rate calculation unit 20c.

FIG. 9 shows the flow of pressure oil in the hydraulic circuit. The thick line in the figure indicates that it is a circuit through which pressure oil flows. Each of the regulators 11a to 18a receives a control signal from the pump/valve control unit 20d via a signal line, and controls the discharge flow rates of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18. The closed circuit pump 11 discharges hydraulic oil to the boom head 1a of the boom cylinder 1 via the flow path switching valve 21c to extend the boom cylinder 1 (closed circuit 11-1). The closed circuit pump 12 discharges hydraulic oil to the hydraulic motor 7 via the flow path switching valve 21c to rotate the hydraulic motor 7 (closed circuit 12-7: first emergency closed circuit).

The hydraulic oil discharged by the open circuit pump 15 flows into the arm head 3a via the rod assist valve 28a, and extends the arm cylinder 3 (emergency switching flow path 50). At this time, the hydraulic oil flowing out from the arm rod 3b flows through the hydraulic oil return flow path 65 through the flushing valve 30a and flows out into the tank 25.

The hydraulic fluid discharged by the open circuit pump 16 flows into the bucket head 5a via the rod assist valve 29a and extends the bucket cylinder 5 (emergency switching flow path 51). At this time, the hydraulic oil flowing out from the bucket rod 5b flows through the hydraulic oil return flow path 65 through the flushing valve 30b and flows out into the tank 25. As a result, all the actuators of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 are simultaneously driven by the single engine 9a.

On the other hand, when the engine 9b is inoperable, when the operator operates all the operation levers 19a to 19d to input the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 in the contracting direction and the hydraulic motor 7 is driven to rotate left, The flow rate calculation unit 20c in the control device 20 shown in FIG. 10 sets the control command value of the flow path switching valve 21c so that the closed circuit pump 11 and the boom cylinder 1 are connected, and the closed circuit pump 12 and the hydraulic motor 7 are connected. To do. Further, the control command values of the rod assist valves 28a and 29a are set to open so that the open circuit pump 15 and the arm rod 3b and the open circuit pump 16 and the bucket rod 5b are connected by a flow path.

The pump/valve control unit 20d outputs control signals to the closed circuit pumps 11 to 14, the open circuit pumps 15 to 18, and the flow path switching valves 21c and 21d according to the control command value from the flow rate calculation unit 20c. Further, the emergency circuit control unit 20e outputs a control signal to the rod assist valves 28a, 29a, 28b, 29b according to the control command value from the flow rate calculation unit 20c. Each of the regulators 11a to 18a shown in FIG. 7 receives a control signal from the pump/valve control unit 20d via a signal line, and controls the discharge flow rates of the closed circuit pumps 11 to 14 and the open circuit pumps 15 to 18.

In FIG. 9, the closed circuit pump 11 discharges hydraulic oil to the boom head 1a of the boom cylinder 1 via the flow path switching valve 21c, and contracts the boom cylinder 1. The closed circuit pump 12 discharges hydraulic oil to the hydraulic motor 7 via the flow path switching valve 21c to rotate the hydraulic motor 7. The hydraulic fluid discharged by the open circuit pump 15 flows into the arm rod 3b via the rod assist valve 28a, and contracts the arm cylinder 3. At this time, the hydraulic oil flowing out from the arm head 3a flows out into the tank 25 via the flushing valve 30a. The hydraulic oil discharged by the open circuit pump 16 flows into the bucket rod 5b via the rod assist valve 29a, and contracts the bucket cylinder 5. At this time, the hydraulic oil flowing out from the bucket head 5a flows out into the tank 25 via the flushing valve 30b. As a result, all actuators of the boom cylinder 1, the arm cylinder 3, the bucket cylinder 5, and the hydraulic motor 7 are driven simultaneously.

Next, the function and effect of the second embodiment will be described. For example, in the first embodiment, a large number of hydraulic devices and their controls are required when the one-sided engine fails, and for example, an assist flow path where the hydraulic oil of the open circuit pumps 15 to 18 and the closed circuit pumps 11 to 14 merges. In order to shut off the valve, it was necessary to provide and close the assist valves 23a to 24b, and to control the connection direction of the auxiliary control valve.

On the other hand, in the second embodiment, the flow passage switching valves 21c and 21d are provided with the merging circuit to the cylinder head side of the open circuit pumps 15 to 18, so that the assist valves 23a to 24b required in the first embodiment are unnecessary. Becomes In addition, since the direction switching function of the auxiliary control valves 26a to 27b is not necessary, a simple switching valve such as the rod assist valves 28a, 28b, 29a, and 29b can be used, thereby lowering the work efficiency when the one-sided engine fails. It is possible to simplify the hydraulic circuit configuration while maintaining the function of suppressing the above, and reduce the mounting cost and the like.

In the above embodiments, the case where the present invention is applied to the hydraulic excavator has been described as an example, but the present invention is also applicable to construction machines other than the hydraulic excavator. For example, the present invention is applicable to general construction machines such as hydraulic cranes equipped with two or more engines, which are equipped with a hydraulic device that drives a plurality of hydraulic cylinders by a closed circuit. Further, it is possible to use a double tilting pump motor instead of the closed circuit pumps 11 to 14. In this case, energy can be regenerated.

1 Boom cylinder (1st hydraulic actuator)
2 boom 3 arm cylinder (first hydraulic actuator)
4 arms 5 bucket cylinder (second hydraulic actuator)
6 bucket 7 hydraulic motor (second hydraulic actuator)
9a, 9b engine (motor)
11, 12 Closed circuit pump (first open circuit pump)
13, 14 Open circuit pump (second open circuit pump)
15, 16 open circuit pump (first open circuit pump)
17, 18 Open circuit pump (second open circuit pump)
19 Operation device 20 Control device 20b Engine failure detection part 21a Flow path switching valve (first closed circuit switching device)
21b Flow path switching valve (second closed circuit switching device)
21c Flow path switching valve (first closed circuit switching device)
21d Flow path switching valve (second closed circuit switching device)
23a, 24a Assist valve (first assist switching device)
23b, 24b Assist valve (second assist switching device)
25 tanks (hydraulic oil tanks)
26a, 27a Auxiliary control valve (first assist switching device)
26b, 27b Auxiliary control valve (second assist switching device)
28a, 29a Rod assist valve (first assist switching device)
28b, 29b Rod assist valve (second assist switching device)
30a, 30b Flushing valve 40, 41 Assist flow path (first assist flow path)
42, 43 assist flow path (second assist flow path)
50, 51 Emergency switching channel (first emergency switching channel)
52, 53 emergency switching flow path (second emergency switching flow path)
62, 66 hydraulic oil return flow path (first hydraulic oil return flow path)
63, 65 hydraulic oil return flow path (second hydraulic oil return flow path)
100 hydraulic excavator (construction machinery)
102 Upper revolving structure 103 Lower traveling structure (running structure)
104 Front working machine (working machine)
HD1 first hydraulic drive HD2 second hydraulic drive

Claims (6)

A first prime mover, a first hydraulic drive device driven by the first prime mover, a plurality of first hydraulic actuators operated by pressure oil supplied from the first hydraulic drive device, a second prime mover, and the second prime mover. A construction machine including a second hydraulic drive device driven by a prime mover, and a plurality of second hydraulic actuators operated by pressure oil supplied from the second hydraulic drive device,
The first hydraulic drive device,
A plurality of first closed circuit pumps and a plurality of first open circuit pumps connected to the first prime mover;
Any one of the plurality of first hydraulic actuators and any one of the plurality of first closed circuit pumps are connected to each other, and pressure oil is generated between the first hydraulic actuator and the first closed circuit pump. A plurality of circulating first closed circuits;
A plurality of connecting any one of the plurality of first closed circuits and one of the plurality of first open circuit pumps to supply pressure oil from the first open circuit pump to the first closed circuit. A first assist flow path of
The second hydraulic drive device,
A plurality of second closed circuit pumps and a plurality of second open circuit pumps connected to the second prime mover;
Any one of the plurality of second hydraulic actuators and any one of the plurality of second closed circuit pumps are connected to each other, and pressure oil is generated between the second hydraulic actuator and the second closed circuit pump. A plurality of circulating second closed circuits;
A plurality of units that connect any one of the plurality of second closed circuits and one of the plurality of second open circuit pumps to supply pressure oil from the second open circuit pump to the second closed circuit. A second assist flow path of
Further, the first assist flow path is branched from any one of the plurality of first assist flow paths, is connected to any one of the plurality of second closed circuits, and is connected to the first assist flow path. At least one first emergency switching passage for supplying pressure oil from an open circuit pump to the second closed circuit;
A first assist switching device for guiding the pressure oil flowing through the first assist channel to the first emergency switching channel;
The second open circuit branching from any one of the plurality of second assist channels, connected to any one of the plurality of first closed circuits, and connected to the second assist channel. At least one second emergency switching passage for supplying pressure oil from the pump to the first closed circuit;
A second assist switching device for guiding the pressure oil flowing through the second assist channel to the second emergency switching channel,
A construction machine comprising: a control device that controls operations of the first assist switching device and the second assist switching device. In claim 1,
Any one of the plurality of second hydraulic actuators and any one of the plurality of first closed circuit pumps are connected to each other, and pressure oil is generated between the second hydraulic actuator and the first closed circuit pump. At least one first closed closed circuit that circulates;
A first closed circuit switching device for guiding pressure oil supplied from the first closed circuit pump and flowing through the first closed circuit to the first emergency closed circuit;
Any one of the plurality of first hydraulic actuators and any one of the plurality of second closed circuit pumps are connected to each other, and pressure oil is generated between the first hydraulic actuator and the second closed circuit pump. At least one second closed emergency circuit that circulates;
A second closed circuit switching device for guiding the pressure oil supplied from the second closed circuit pump and flowing through the second closed circuit to the second emergency closed circuit;
The construction machine, wherein the control device controls operations of the first closed circuit switching device and the second closed circuit switching device. In claim 2,
The control device includes an engine failure detection unit that detects a failure of the first prime mover and the second prime mover,
The control device is
When the engine failure detection unit determines that the second prime mover is inoperable,
The operation of the first assist switching device is controlled to switch the pressure oil flowing through the first assist flow passage to the first emergency switching flow passage, and the operation of the first closed circuit switching device is controlled. The pressure oil supplied from the first closed circuit pump and flowing through the first closed circuit is switched to be guided to the first emergency closed circuit, and the plurality of first closed circuit pumps and the plurality of first closed circuit pumps are switched. The 1-open circuit pump supplies pressure oil to all of the plurality of first hydraulic actuators and the plurality of second hydraulic actuators so that the hydraulic actuators can operate.
When the engine failure detection unit determines that the first prime mover is inoperable,
The operation of the second assist switching device is controlled to switch the pressure oil flowing through the second assist flow passage to the second emergency switching flow passage, and the operation of the second closed circuit switching device is controlled. The pressure oil supplied from the second closed circuit pump and flowing through the second closed circuit is switched to the second emergency closed circuit, and the plurality of second closed circuit pumps and the plurality of second closed circuit pumps are switched. The two-open circuit pump supplies pressure oil to all of the plurality of first hydraulic actuators and the plurality of second hydraulic actuators so that the respective hydraulic actuators can operate. Construction machinery. In claim 3,
A hydraulic oil tank for storing hydraulic oil,
A first hydraulic oil return flow path for returning the pressure oil supplied from the first open circuit pump through the first emergency switching flow path to the second hydraulic actuator to the hydraulic oil tank;
And a second hydraulic oil return flow path for returning the pressure oil supplied from the second open circuit pump through the second emergency switching flow path to the first hydraulic actuator to the hydraulic oil tank. Construction machine characterized by. In claim 4,
A traveling body, a hydraulic motor for driving the traveling body, an upper revolving body rotatably provided on the traveling body, and a boom and a boom cylinder for driving the boom, the upper revolving body being provided so as to be able to descend and descend. And an arm, an arm cylinder for driving the arm, a bucket, and a work machine having a bucket cylinder for driving the bucket,
The plurality of first hydraulic actuators include the boom cylinder and the arm cylinder,
The plurality of second hydraulic actuators include the bucket cylinder and the hydraulic motor,
The control device is
When the engine failure detection unit determines that the second prime mover is inoperable, the operation of the first assist switching device and the first closed circuit switching device is controlled to control the plurality of first closed circuits. A construction machine characterized in that a pump operates the boom cylinder and the hydraulic motor, respectively, and a plurality of first open circuit pumps operate the arm cylinder and the bucket cylinder, respectively. In claim 5,
Further comprising an operating device for operating the working machine,
The control device controls operations of the first assist switching device, the second assist switching device, the first closed circuit switching device, and the second closed circuit switching device according to an operation amount of the operating device. A construction machine characterized by that.